# Draft California 2012 Integrated Report( 303(d) List/305(b) Report)

# Supporting Information

## Regional Board 6 - Lahontan Region

Water Body Name: | Cow Head Slough
Water Body ID: | CAR6420001120080811005235
Water Body Type: | River & Stream

DECISION ID | 25786 | Region 6
Cow Head Slough

Pollutant: | Dissolved oxygen saturation
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. The single sample exceeds the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 or Table 3.2 of the Policy. 3. The single sample exceeded the water quality objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 25786, Dissolved oxygen saturation | Region 6
Cow Head Slough
LOE ID: | 25760
Pollutant: | Dissolved oxygen saturation
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Dissolved
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 1
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The dissolved oxygen saturation in one sample was 62 percent.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The applicable objective from the Lahontan Basin Plan states: "The dissolved oxygen concentration shall not be depressed by more than 10 percent, below 80 percent saturation, or below 7.0 mg/L at any time, whichever is more restrictive." (Note: this is a watershed-specific narrative objective that differs from the regionwide objectives in Basin Plan Table 3-6.)
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 26028 | Region 6
Cow Head Slough

Pollutant: | Nitrate
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. The single nitrate sample does not exceed the California Maximum Contaminant Level (MCL). No biological data are available to assess whether it exceeds the water quality objective for biostimulatory substances. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 or Table 3.1 of the Policy. 3. The single sample did not exceed the MCL and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. The sample was insufficient to determine whether the biostimulatory substances objective was exceeded. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 26028, Nitrate | Region 6
Cow Head Slough
LOE ID: | 25763
Pollutant: | Nitrate
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Municipal & Domestic Supply
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The concentration of NO3-N in one sample was 0.07 mg/L. The MCL was not exceeded.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for nitrate is 45 mg/L expressed "as nitrate," equivalent to 10 mg/L expressed "as N.".
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):
Line of Evidence (LOE) for Decision ID 26028, Nitrate | Region 6
Cow Head Slough
LOE ID: | 25764
Pollutant: | Nitrate
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Dissolved
Beneficial Use: | Cold Freshwater Habitat
Aquatic Life Use: | Marine Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The concentration of NO3-N in one sample was 0.07 mg/L
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The Lahontan Basin Plan does not include site specific objectives for this water body. The regionwide narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 25787 | Region 6
Cow Head Slough

Pollutant: | Oxygen, Dissolved
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. The single sample exceeds the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 or Table 3.2 of the Policy. 3. The single sample exceeded the water quality objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 25787, Oxygen, Dissolved | Region 6
Cow Head Slough
LOE ID: | 25759
Pollutant: | Oxygen, Dissolved
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Dissolved
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 1
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The dissolved oxygen concentration in one sample was 5.57 mg/L.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The applicable water quality objective (from Lahontan Basin Plan Table 3-6) is a 1 day minimum dissolved oxygen concentration of 8 mg/L.
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 25640 | Region 6
Cow Head Slough

Pollutant: | Phosphate
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. No biological data are available to determine whether the single phosphate sample exceeds the water quality objective for biostimulatory substances. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 or Table 3.1 of the Policy. 3. No biological data are available to determine compliance with the objective. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 25640, Phosphate | Region 6
Cow Head Slough
LOE ID: | 25766
Pollutant: | Phosphate
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | Dissolved
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The concentration of PO4-P in one sample was 0.03 mg/L
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The Lahontan Basin Plan does not include site specific objectives for this water body. The regionwide narrative objective for biostimulatory substances states: "Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect the water for beneficial uses."
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 25754 | Region 6
Cow Head Slough

Pollutant: | Sediment
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: One line of evidence is available in the administrative record to assess this pollutant. . The narrative water quality objective for sediment is an antidegradation-based objective and the single sample is insufficient to document baseline and trend conditions as required under Listing Policy Section 3.10. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. The requirements of Listing Policy section 3.10 to document baseline and trend conditions are not met in relation to the narrative water quality objective. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 25754, Sediment | Region 6
Cow Head Slough
LOE ID: | 25767
Pollutant: | Sediment
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The concentration of suspended sediment in one sample was 48.6 mg/L
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The Lahontan Basin Plan's narrative objective states: "The suspended sediment load and suspended sediment discharge rate of surface waters shall not be altered in such a manner as to cause nuisance or adversely affect the water for beneficial uses."
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 25753 | Region 6
Cow Head Slough

Pollutant: | Specific Conductance
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the section 303(d) list under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. One line of evidence ia available in the administrative record to assess this pollutant. The single sample does not exceed the water quality objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do satisfy the data quantity requirements of section 6.1.5 or Table 3.2 of the Policy. 3. The single sample did not exceed the water quality objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 25753, Specific Conductance | Region 6
Cow Head Slough
LOE ID: | 25757
Pollutant: | Specific Conductance
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Municipal & Domestic Supply
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. A single specific conductance measurement was 302 uS/cm.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for specific conductance is 900 microsiemens per centimeter (uS/cm).
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One specific conductance measurement was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 25764 | Region 6
Cow Head Slough

Pollutant: | Temperature, water
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: One line of evidence is available in the administrative record to assess this pollutant. . The narrative water quality objective for temperature is an antidegradation-based objective and the single sample is insufficient to document baseline and trend conditions as required under Listing Policy Section 3.10. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. The requirements of Listing Policy section 3.10 to document baseline and trend conditions are not met in relation to the narrative water quality objective. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 25764, Temperature, water | Region 6
Cow Head Slough
LOE ID: | 25765
Pollutant: | Temperature, water
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The temperature in one sample was 20.86 degrees Celsius.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The temperature objective in the Lahontan Basin Plan states: "The natural receiving water temperature of all waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such an alteration in temperature does not adversely affect the water for beneficial uses. For waters designated WARM, water temperature shall not be altered by more than five degrees Fahrenheit ... above or below the natural temperature. For waters designated COLD, the temperature shall not be altered. Temperature objectives for COLD interstate waters and WARM interstate waters are as specified in the 'Water Quality Control Plan for Control of Temperature in The Coastal and Interstate Waters and Enclosed Bays and Estuaries of California' including any revisions."
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One sample was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 26088 | Region 6
Cow Head Slough

Pollutant: | Turbidity
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Sources: | Source Unknown
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Two lines of evidence are available in the administrative record to assess this pollutant. The single sample exceeds the California Maximum Contaminant Level (MCL) and this does not exceed the allowable frequency in Listing Policy Table 3.2. The narrative water quality objective for turbidity is an antidegradation-based objective and the single sample is insufficient to document baseline and trend conditions as required under Listing Policy Section 3.10. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 or Table 3.2 of the Policy. 3. The requirements of Listing Policy section 3.10 to document baseline and trend conditions are not met in relation to the narrative water quality objective. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains the same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 26088, Turbidity | Region 6
Cow Head Slough
LOE ID: | 25761
Pollutant: | Turbidity
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The turbidity in one sample was 43.5 NTU.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The Lahontan Basin Plan's regionwide turbidity objective states: "Waters shall be free of changes in turbidity that cause nuisance or adversely affect the water for beneficial uses. Increases in turbidity shall not exceed natural levels by more than 10 percent."
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One turbidity measurement was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):
Line of Evidence (LOE) for Decision ID 26088, Turbidity | Region 6
Cow Head Slough
LOE ID: | 25762
Pollutant: | Turbidity
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Municipal & Domestic Supply
Number of Samples: | 1
Number of Exceedances: | 1
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. The turbidity in one sample was 43.5 NTU.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | California Maximum Contaminant Levels apply to ambient waters under the Lahontan Basin Plan's "Chemical Constituents" objective. The MCL for turbidity is 5 NTU.
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One turbidity measurement was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):

DECISION ID | 26015 | Region 6
Cow Head Slough

Pollutant: | pH
Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision: | Do Not List on 303(d) list (TMDL required list)(2010)
Revision Status | Original
Impairment from Pollutant or Pollution: | Pollutant
Regional Board Staff Conclusion: | Regional Board Conclusion: This pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: One line of evidence is available in the administrative record to assess this pollutant. The narrative water quality objective for pH is an antidegradation-based objective and the single sample is insufficient to document baseline and trend conditions as required under Listing Policy Section 3.10. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the section 303(d) list in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used do not satisfy the data quality requirements of section 6.1.4 of the Policy. 2. The data used do not satisfy the data quantity requirements of section 6.1.5 of the Policy. 3. The requirements of Listing Policy section 3.10 to document baseline and trend conditions are not met in relation to the narrative water quality objective. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.
Regional Board Staff Decision Recommendation: | No new data were assessed for this assessment cycle. The conclusion reached in the previous cycle remains in same. The Regional Board will update this decision when new data and information become available in a future assessment cycle.

Line of Evidence (LOE) for Decision ID 26015, pH | Region 6
Cow Head Slough
LOE ID: | 25758
Pollutant: | pH
LOE Subgroup: | Pollutant-Water
Matrix: | Water
Fraction: | None
Beneficial Use: | Cold Freshwater Habitat
Number of Samples: | 1
Number of Exceedances: | 0
Data and Information Type: | Fixed station physical/chemical (conventional plus toxic pollutants)
Data Used to Assess Water Quality: | The U.S. Bureau of Land Management sampled this station in July 2002. One pH measurement was 8.1 units.
Data Reference: | Water quality data for surface waters on U.S Bureau of Land Management lands in Lassen and Modoc Counties
SWAMP Data: | Non-SWAMP
Water Quality Objective/Criterion: | The Lahontan Basin Plan's regionwide water quality objective states: "In fresh waters with designated beneficial uses of COLD or WARM, changes in normal ambient pH levels shall not exceed 0.5 pH units. For all other waters of the region, the pH shall not be depressed below 6.5 nor raised above 8.5 units. The Regional Board recognizes that some waters of the Region may have natural pH levels outside of the 6.5 to 8.5 range. Compliance with the pH objective for these waters will be determined on a case-by-case basis."
Objective/Criterion Reference: | Water Quality Control Plan for the Lahontan Region (as amended)
Evaluation Guideline: |
Guideline Reference:
Spatial Representation: | One station was sampled.
Temporal Representation: | One pH measurement was taken on July 22, 2002.
Environmental Conditions: | Cow Head Slough is the natural outlet stream of Cow Head Lake in northeastern Modoc County, and flows north into Oregon. (Although the spelling "Cowhead" is used in the Basin Plan and other documents, the correct geographic name uses two words.) The lake and slough have been hydromodified for agriculture and the lake bed is now pumped dry so that crop can be grown upon it. The slough and irrigation canals on the lake bed are habitat for the fish subspecies Cowhead Lake tui chub, a California Species of Special Concern found only in this watershed. Cow Head Slough is designated for both the Warm Freshwater Habitat and Cold Freshwater Habitat beneficial uses, and for the Rare, Threatened or Endangered Species and the Spawning, Reproduction and Development uses.
QAPP Information: | No quality assurance information was submitted with the data.
QAPP Information Reference(s):